Genetic polymorphisms of the major histocompatibility complex-encoded antigen-processing genes TAP and LMP in sarcoidosis

Sarcoidosis is a granulomatous disease showing a significant increase in the HLA-DRS, -DR6, and -DR8 associated alleles in Japanese. To investigate whether the class I antigen-processing genes, encoded within the MHC class II region between the HLA-DP and -DQ loci, are involved in determining the susceptibility to sarcoidosis, TAP1, TAP2, and LMP2 alleles were analyzed by the PCR-RFLP method in 85 Japanese patients with sarcoidosis and 91 healthy controls. There were no significant differences in the distribution of TAP1 and LMP2 alleles between the subgroups of the patients and controls positive or negative for DR5, DRG, and DR8. A significant decrease in the frequency of TAP2*0201 was found among the patients negative for DR5, DR6, and DR8 as compared to the DR-matched controls (p < 0.05), but this could be explained by its linkage disequilibrium to the negatively associated allele DR1. These findings suggest that the TAP or LMP2 gene is not primarily involved in the susceptibility to sarcoidosis. In the course of this study, a linkage disequilibrium was observed in the Japanese population between TAP1 and TAP2 alleles, TAP1*0201 and TAP2*0102.